[Fwd: Re: Breaking wafers?]

Mary Tang mtang at snf.stanford.edu
Wed Sep 8 14:18:39 PDT 2004

Hi everyone!

Thanks for your inputs!  I think Karl has provided the historical
perspective, and explains why a larger diameter is useful.  So, I'll
change the operating procedure to reflect these inputs (with the
recommendation to run at 150 mm, whatever the substrate size,
recognizing that this negates the entry speed feature).  By the way,
this morning I tried using 200 mm as suggested by some, but it seems
that the stage sometimes gets stuck because it's hit a limit switch - so
based on this, I think 150 mm might be better (please let me know if
your experience suggests otherwise!)

Thanks again --


-------- Original Message --------
Subject: Re: Breaking wafers?
Date: Tue, 7 Sep 2004 17:38:15 -0700 (PDT)
From: Karl Brandt <brandt at snf.stanford.edu>
To: Mary Tang <mtang at snf.stanford.edu>

Believe it or not, this was a problem from the first day we got the tool
from K&S. After repeated attempts by K&S to resolve it, they finally
up their hands and said they simply had no idea what was wrong or how to
fix it. The accepted workaround has been to set the wafer diameter to
large diameter.


Karl Brandt                                            

On Tue, 7 Sep 2004, Mary Tang wrote:

> Hi everyone --
> "rosti" dropped by my office to say that he was thinking about using the
> wafersaw, but was concerned about a problem he had experienced a couple
> of times in which the saw BROKE his wafer.  He says that instead of
> starting on the edge, in these instances, the saw blade dropped onto the
> middle of the wafer and thus broke his wafers.  The last instance that
> he observed was some time back last October or so.
> Now I'm worried!  Usually, when a wafer is ready for dicing, you've
> expended a lot of time and energy into it -- you simply can't afford to
> have it smashed.  I'm also really concerned because I've been training
> on the wafersaw for a couple of years now, but have not observed this
> problem nor had I heard about it from anyone (and here I thought I knew
> all the machine's quirks).  I had heard that it used to be a problem,
> but not seen since the system was basically rebuilt a few years ago.
> Now, I'm hearing otherwise...
> Has anyone else had this problem?  If so, could you let me know
> approximately when it happened and how often (if you were "lucky", like
> rosti, and got hit more than once?)  And maybe even the circumstances
> when it occurred (if you remember).  Your feedback will help us decide
> what to do (if the darned thing is breaking wafers intermittently, we
> may need to take it off-line...)
> And, most importantly, if you observe this or any other problem, please,
> please, please report it on Coral!  (I'm going back several years, and
> don't happen to see anything about the machine breaking wafers...)
> Thanks,
> Mary
> --
> Mary X. Tang, Ph.D.
> Stanford Nanofabrication Facility
> CIS Room 136, Mail Code 4070
> Stanford, CA  94305
> (650)723-9980
> mtang at stanford.edu
> http://snf.stanford.edu

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